AutoCAD LT AutoLISP MCP Server

What is AutoCAD LT AutoLISP MCP Server?

An MCP server that automates AutoCAD LT and generates DXF files headless. It provides two backends—File IPC (requires AutoCAD LT 2024+ on Windows) and ezdxf (any platform, no AutoCAD needed)—and exposes 8 consolidated tools over the MCP stdio transport, enabling an MCP client to drive AutoCAD through natural-language requests.

How to use AutoCAD LT AutoLISP MCP Server?

Clone the repository, install dependencies with uv sync, load mcp_dispatch.lsp in AutoCAD LT via APPLOAD, then configure your MCP client (e.g., Claude Desktop) with the command pointing to the Python interpreter in the project venv. Set the AUTOCAD_MCP_BACKEND environment variable to auto, file_ipc, or ezdxf. Verify by calling system(operation="status") from the client.

Key features of AutoCAD LT AutoLISP MCP Server

• Two backends: File IPC (AutoCAD LT required) and ezdxf (headless, any platform)
• 8 consolidated tools: drawing, entity, layer, block, annotation, pid, view, system
• Focus‑free automation: sends keystrokes without stealing window focus
• Arbitrary AutoLISP execution via execute_lisp
• Headless DXF generation with matplotlib rendering
• Screenshot capture even when AutoCAD is minimized

Use cases of AutoCAD LT AutoLISP MCP Server

• Automate drawing creation and modification in AutoCAD LT using natural language
• Generate DXF files headless on any platform (Linux, macOS, WSL)
• Insert P&ID symbols from the CAD Tools Online library
• Manage layers, blocks, and annotations programmatically
• Run custom AutoLISP scripts through the MCP interface

FAQ from AutoCAD LT AutoLISP MCP Server

Do I need AutoCAD LT installed to use this server?

Only for the File IPC backend. The ezdxf backend works on any platform without AutoCAD.

Can I use the File IPC backend on macOS?

No. AutoLISP support in AutoCAD LT is Windows‑only (LT 2024+). AutoCAD LT for Mac does not support AutoLISP.

How does the server communicate with AutoCAD?

The File IPC backend writes JSON commands to a shared directory (default C:/temp) and sends keystrokes to AutoCAD’s MDIClient window via PostMessageW(WM_CHAR), triggering the (c:mcp-dispatch) AutoLISP command.

Which MCP transport does this server use?

Stdio (JSON‑RPC). No authentication is described.

Does the ezdxf backend support all operations?

No. Operations such as offset, fillet, chamfer, plot_pdf, undo/redo, and some P&ID operations are File IPC only.